Method of unhajbing skins



3,103,459 Patented Sept. 10, 1963 3,103,469 METHOD OF UNHAIRING SKINS AND HIDES Otto Grimm, Darmstadt, Germany, assigfior to Rohm & Haas G.m.b.ll., Darmstadt, Germany N Drawing. Filed May 23, 1961, Ser. No. 111,909 8 Claims. (Cl. 1956) This invention relates to the treatment of skins and hides, more particularly to the depilation of skins and hides with the aid of proteolytic enzymes.

It is already well known from German Patent No. 268,873, that skins and hides can be depilated by the action of pancreas tryptase. In accordance with processes described in this pioneer patent, softened skins and hides are treated in a tryptase-containing bath for several days whereupon an acceptable loosening of the hair is achieved only if the hides are pretreated with caustic soda. A significant advance was achieved over this method by the use of proteolytic enzymes in powder form applied to green or softened skins and hides for unhairing or dewooling, this improved process being described in German Patent No. 1,026,038. It has furthermore been suggested that skins and hides which have been presoftened with water and after-treated for further softening with a powder or paste form of a proteolytic enzyme can be depilated by treatment with inorganic neutral salts of alkali metals and ammonium. The addition of sulfur compounds having a reducing action, especially oxygen-containing sulfur compounds, has also been found to be advantageous. The use of non-ionic wetting agents in the pre-softening treatment is necessary in this process.

It has now been found that the depilating action of proteolytic enzymes in the previously proposed processes can be improved significantly by the use of phthalic acid or phthalic acid derivatives. This increased activation of the proteolytic enzymes has been found to take place with a phthalic acid, i.e., ortho-phthalic acid, isophthalic acid, or terephthalic acid, the salts of these acids as well as the esters and other derivatives of these acids so long as they do not contain sulfonic acid groups. Phthalimide has been found to be particularly effective. The increased enzymatic activity due to the presence of the activators is most surprising in view of the fact that the activators are either difliculty or, as in the case of phthalimide, barely soluble in water. It has been found to be particularly advantageous to activate proteases in this manner which are applied in powder form without the addition of water by the method of German Patent No. 1,026,038. Thus, for example, if softened and dripped calfskins are agitated for 15 minutes with 1% by weight mold fungus protease and 0.1% phthalimide as activator, said percentages being calculated on the weight of softened hide, the desired hair loosening is appreciably better than that obtained with twice that amount of protease but no activator. Whereas an addition of ammonium sulfate, sodium sulfite and sodium chloride, as suggested in German Patent No. 1,026,038, results in some desirable increase in activity Within definite limits which cannot be exceeded by the use of larger quantities of these addition agents, further improvement is nevertheless possible by the use of phthalic acid and its derivatives.

Activation of enzymatic activity in accordance with the invention by addition of activators, especially phthalimide, is also applicable to earlier suggested processes which involve pretreating softened skins and hides with an insufficient amount of proteolytic enzym for depilation and then applying to the skins and hides inorganic neutral salts of alkali metals or ammonium. In these circumstances, an especially rapid and fluid depilation is achieved. It is particularly suprising that a rapid and complete hair loosening can be achieved by after-treating,

with phthalic acid or its derivatives, skins and hides that have been pretreated with enzymes. To summarize, the activators of the invention have the desired effect whether they are combined directly with the hair loosening proteolytic enzymes or whether they are applied before or after the enzymatic treatment of the skins and hides.

it is within the scope of the invention to combine the use of the activators of the invention with already-known or previously proposed activators, e.g., reducing oxygencontaining sulfur compounds, neutral salts and the like. Thus, for example, red and white steerhides that have been softened and drained can be depilated with case after 24 hours if they are agitated for 15 minutes with 1.8% mold fungus protease, 0.1% phthalimide, 0.2% ammonium sulfate, 0.5% sodium sulfite, and 0.15% sodium chloride, each amount being calculated on the basis of the softened weight of the skins.

The proteolytic enzymes which are useful in combination with the activators of the invention for depilating skins and hides include particularly the proteolytic enzymes of microorganisms such as mold fungus protease derived from Aspergillus-types, pancreatic tryptase, and bacterial proteases, especially of the subtilis strain. These enzymes are preferably combined with oligases, i.e. with enymes which have a splitting action only on disaccharides and lower polysaccharides, e.g. with glucosidases and galactosidases found in almond emulsin (synaptase).

The amount of activators added in accordance with the method of the invention may vary within wide limits, very small amounts resulting in significant improvements in results and substantial amounts being unharmful. Generally, amounts between about 0.05 and about 5 percent by weight of the hide are operable and adequate, amounts within the range of about 0.1 to 1% being preferred.

The amount of enzyme may also vary considerably, quantities ranging from a fraction of a percent to several percent, e.g. about 0.1 to about 5% being operable, and amounts of the order of about 0.5 to 3.5% being preferred.

The method of the invention can be carried out under weakly acid, neutral or alkaline conditions, a pH within the range of about 5.5 to about 7.5 being preferred for optimum results. One preferred embodiment of the method of the invention is to agitate salted or unsalted, presoftened, washed and drained hides with a suitable enzyme and activator for about thirty minutes to an hour and then allow them to lie for about a day before unhairing. In accordance with another embodiment, washed hides are pretreated with activator, if desired in a bath, and then subjected to enzymatic action after draining olf most of the liquor and finally allowed to lie for about a day before depilation. It is also possible, as shown in the examples forming part of this specification, to carry out the enzymatic treatment in water with the activator added before or with the enzyme.

It is to be understood, of course, that the method of the invention can be altered in any manner well understood by those skilled in the art, eg by use of preservative or wetting agents that are compatible with the enzymes, the combination of the new activators of the invention with other addition products known to increase the activity of the enzymes, with powderor paste-form unhairing enzyme products and with treating baths containing various enzymes and activators.

The advantages and utility of the invention will become further apparent from the following examples, in which the protease products referred to are those having an enzyme value of approximately 5,000 as determined in accordance with A. Kuntzel, Gerbereichemisches Taschenbuch, Sixth Edition, Theodor Stcnikopf, publisher,

Dresden and Leipzig (1955), page 86, and the amounts are given in terms of percent by weight of the skins or hides treated.

Example 1 Salted, red and white steerhides, softened with water, washed and drained, were agitated for one hour with 2.0% mold fungus protease,

0.1% phthalimide, and

0.2% calcined sodium carbonate,

without the addition of water at a pH of 7.5. After 24 hours the hides were readily depilated.

Example 2 Black and white steerhides, softened with water, washed and drained, were drummed for thirty minutes with 2.0% mold fungus protease,

0.1% orthophthalic acid,

0.1% sodium phthalate dihydrate, and

0.1% phtbalimide,

at a pH of 6.5. After lying for 24 hours, the hides were readily depilated.

Example 3 Red and white, salted steerhides softened with water, washed and then drained, were drummed for one hour with pancreas tryptase, calcined sodium carbonate, 1.0% ammonium chloride, and 0.1% Phthalimide, at a pH of 7.5. After lying for 24 hours, the hides were readily depilated.

Example 4 Black and white, salted steerhides softened and washed with water and drained, were drummed for one-half hour with bacterial protease in the presence of oligase, calcined sodium sulfite,

ammonium sulfate,

0.2% calcined sodium bisulfite, and

0.3% phthalimide,

at a pH of 6.5. After lying for 24 hours, the hides were readily depilated.

Example 5 Fresh sheepskins were washed in running water at 35 C. for ten minutes to remove blood and dirt and then paddled for thirty minutes with 0.5% phthalirnide in 300% by weight, based on the green weight of the hides, of water at 35 C. After thirty minutes, the hides were piled, drained and then sprinkled on the fleshy side with 2.5% mold fungus protease,

0.25% calcined sodium bisulfite,

0.25% ammonium sulfate, and

0.06% of preservative, based on the green weight of the hides.

The hides were readily dewooled after 24 hours.

Example 6 Salted, black and white steerhides, softened with water, washed and drained, were drummed for thirty minutes with 2% mold fungus protease,

1% terephthalic acid, and 0.3% calcined sodium carbonate,

at a pH of 5.5. The hides were readily depilated after lying for 24 hours.

Example 7 Water-softened and washed, dried Indian goatskins were drummed for one hour with 300% water at 20 C., 2% mold fungus protease, and 1% sodium phthalate monohydrate.

The activity of the mold fungus protease took place at a pH of 7.0. After lying for 36 to 48 hours, the skins were readily depilated.

Example 8 Water-softened and washed, dried Indian goatskins were drummed for one hour with 300% water and 1.2% torephthalic acid. Thereafter,

3.0% mold fungus protease,

0.75% ammonium sulfate,

0.25% calcined sodium white, and 6.5% calcined sodium carbonate,

were added and the hides were drummed for an additional hour. The activity of the mold fungus protease took place at pH 10.5 to 11.0. After 24 hours the skins were readily depilated.

Example 9 Water-softened, salted and drain, red and white calfskins were drummed for one hour with 0.4% bacterial protease with oligases, 0.2% calcined sodium sulfite,

0.4% ammonium sulfate,

0.05% phthalic acid anhydridc, 0.02% sodium bicarbonate, and 0.03% phthalimide.

The activity of the bacterial protease took place at a pH of 7.0. After 24 hours the hides were readily depilated.

What is claimed is:

1. A method of unhairing hides which comprises treating hides with a proteo-lytic enzyme and phthalimide as an activator therefor.

2. The method defined in claim 1 wherein the activator is in an amount between about 0.05 and about 5% by weight of the hide.

3. The method defined in claim 1 wherein the activator is in an amount between about 0.1 and about 1% by weight of the hide.

4. The method defined in claim 1 wherein the activator is applied to the hide simultaneously with the enzyme.

5. The method defined in claim 1 wherein the activator is applied to the hide before treatment with the enzyme is begun.

6. The method defined in claim 1 wherein the activator and enzyme are applied, without the use of additional water, to a hide that has been presoft-ened, washed and drained.

7. The method defined in claim 1 wherein a washed hide is treated with the activator in water and then treated with the enzyme.

8. The method defined in claim 1 wherein the activator is agitated in water containing the activator and the enzyme.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF UNHAIRING HIDES WHICH COMPRISES TREATING HIDES WITH A PROTEOLYTIC ENZYME AND PHTHALIMIDE AS AN ACTIVATOR THEREFOR. 